1. Field of the Invention
The present invention relates to a transducer used in water, and more particularly, to a pressure-balanced underwater acoustic transducer configured not to be affected by the depth of water at which the water pressure is applied to both ends of an oscillating unit, preventing displacement or transformation of the unit due to water pressure.
2. Description of the Related Art
In general, a conventional underwater acoustic transducer having a uni-directionality, as shown in FIG. 1, includes an acoustic window 14 capable of transmitting sound to the front surface of an oscillator 13. The oscillator 13 oscillates by an electrical signal supplied to electrodes and sound waves generated at the oscillator 13 propagate through the water.
A piezoceramic element is generally used as the oscillator 13, and polyurethane or plastic layer is used as the acoustic window 14. A sound-absorbing material 12, usually cork or foam, serving to absorb sound is provided at the rear surface of the oscillator 13. The conventional transducer of the type described herein is incorporated, in general, in a housing 11 thereof and is mostly operated in the surface or shallow depth of water where the displacement or transformation of the transducer is negligible.
In the above-described conventional underwater acoustic transducer, a pressure is applied uni-directionally, that is, only to the front surface of the acoustic window 14. Thus, the operating depth of water and usage time of the transducer are limited depending on the pressure under which the sound-absorbing material 12 can withstand.
Since there is nearly no sound-absorbing material that can withstand underwater as deep as several thousands of meters, the conventional underwater transducer employs a specific plastic layer having a high strength in place of the sound-absorbing material 12.
Since the plastic layer transmits sound well, the sound propagated into the rear surface of the oscillator 13 is transmitted through the plastic layer and reflected back from the housing 11 of the transducer. The reflected sound is combined with the sound propagated to the front surface of the oscillator 13 and travels into water. During combination of two sound waves, phases of the two sound waves must be the same. To this end, it is necessary to adjust the thickness of the plastic layer disposed at the rear surface of the oscillator 13.
However, it is quite difficult to form a plastic layer withstanding at a high pressure. It is also difficult to adjust the thickness of the plastic layer. Thus, it is not easy to manufacture an underwater acoustic transducer for deep sea and high cost is required to manufacture the same. Also, since a pressure is applied in one direction of the transducer, its acoustic characteristics may change according to the depth of water.
To solve the above-described problems, it is an object of the present invention to provide a pressure-balanced underwater acoustic transducer configured not to be affected by the pressure applied to the transducer and to be least affected by the depth of water.
To accomplish the above object of the present invention, there is provided an underwater acoustic transducer including an oscillator unit having an oscillator oscillating by an electrical signal supplied to electrodes, provided on its surface, a sound transmission material for transmitting sound from the oscillator, provided at its periphery, and a transducer housing provided at the exterior of the sound transmission material, a sound reflector positioned over the oscillator unit, for reflecting sound propagated from the oscillator, a water entry layer forming a space between the oscillator unit and the sound reflector to allow water to enter and exit to the rear window of the oscillator, thereby leading to a balanced state of pressures applied to the front and rear windows of the oscillator unit, and a phase combiner for combining sound reflected from the sound reflector and straight traveling sound generated from the front surface of the oscillator into one single phase.
In the present invention, the transducer housing forming the external shape of the oscillator unit and a sound reflector body forming the external shape of the sound reflector are separatably connected to each other, and the phase of the sound reflected from the sound reflector is adjusted by varying the thickness of the water entry layer according to the distance between connected surfaces of the transducer housing and the sound reflector body.
Also, in order to supply an electrical signal to electrodes of the oscillator, a pin connector is installed at the exterior of the transducer housing using a rubber ring for isolation from water.